1. Field of the Invention
This invention relates to a pattern having superior abrasion resistance, and more particularly, to an improvement in the abrasion resistance of a pattern used in the production of a sandmold which is used as a mold for casting.
A sandmold is generally prepared by using a pattern, such as, for example, a wooden, synthetic resin, aluminium, or cast iron pattern. The pattern is liable to be subjected to great abrasion from the filler, including silica, and also from the casting sand when the sandmold is produced.
This invention concerns technology to decrease the abrasion and damage to the surface of a pattern caused by the filler, and to improve its durability.
2. Description of Prior Art
There have been introduced the following methods for improving the durability of the pattern for a sandmold:
(1) A method in which shellac or the like is coated on a pattern (page 92, Casting 1, published by Seibundo Shinkosha Co., Ltd., Jan. 31, 1966), and PA1 (2) A method in which a coating composed mainly of urethane is coated on a pattern (page 80, A Casting Handbook, published by the JAPAN FOUNDATION CASTING ASSOCIATION, May 20, 1973).
However, a pattern having superior durability has not been obtained, and only temporary protection of the surface has been obtained.
Further, a lubricative coating has been disclosed, in which the lubricative powder, for instance, molybdenum disulfide or the like, is added into the coating, and which powder is applied on a wooden pattern (Japanese Patent Publication No. 17568/73). However, this coating has aimed at improving, mainly by a lubricative effect, the drawing of a pattern from a sandmold and a pattern durable for repeated use for the long term has not been obtained.
Furthermore, there have been various other methods used before now. For instance, there has been used a method of applying chrome plating on a raw material to improve the abrasion resistance (Japanese Patent Publication No. 15006/69), or a method of flame coating of a ceramic material at a temperature of 1000.degree. C. or more to provide a ceramic layer. However, both methods need a particular processing treatment, and whether these methods can be used or not depends on the inherent properties of the pattern or its shape.